The invention relates to a motor vehicle door lock, hood lock or the like.
The invention can be applied to motor vehicle door locks, motor vehicle hood locks, hatch locks, etc. and the definition of motor vehicle door lock should always be understood in this encompassing sense.
In convention motor vehicle door locks (as disclosed in German published application DE-A-29 36 977) the rotary latch made as a fork latch is pivotally mounted on a bearing journal and the tensioned or pressurized detent pawl is swivel-mounted around a detent pawl journal which is located parallel to the bearing journal. The detent pawl is made in one piece, strong and massive, and has a large-area opposing catch surface. The opposing catch surface executes an arc-shaped motion as soon as the detent pawl is actuated by lifting.
Safety aspects with the door closed for a crash have led not only to the rotary latch and the detent pawl being made very massive, but also to an undercut being located between the catch surface and the opposite catch surface (as disclosed in German published application DE-A-32 42 527). The larger the undercut angle, the greater the operating safety of the motor vehicle door lock in case of a crash.
The relatively large engagement depth of the opposing catch surface on the detent pawl into the catch surface on the rotary latch also contributes to increasing the operating safety of the motor vehicle door lock in case of a crash.
The increase of the operating safety of the motor vehicle door lock is achieved with considerable loss of ease of operation. Lifting of the detent pawl requires a large force.
The aforementioned problem was already recognized in the prior art and led to the one-part detent pawl having been replaced by a two-part detent pawl arrangement which can be bent in the middle (as disclosed in European published application EP-A-0 406 77; and German patent DE-C 41 02 049). There are also a large engagement depth and large undercut angle between the detent pawl and the rotary latch with the motor vehicle door closed with high operating safety of the motor vehicle door lock, nevertheless the lifting motion of the detent pawl requires relatively little force, since the detent pawl arrangement bends in the middle when the detent pawl is lifted and in this way the detent pawl executes, not pure arc motion around the detent pawl journal, but knuckle joint-like motion superimposed from arc motions.
In the aforementioned prior art from which the invention proceeds, a reduction of opening forces is achieved with high operating safety. The operating safety of the lock in the case of a crash or also during normal operation is greatly influenced by a second factor, specifically by the problem of false closing.
It has been found that existing classical rotary latches/detent pawl structures occasionally lead to false closing. This means that the detent pawl has therefore dropped only to a small extent, the engagement depth between the catch surface and opposing catch surface is therefore not fully used. The motor vehicle door seems to be closed, when vibration movements occur or in case of a crash however it bursts open unexpectedly. The aforementioned undercut between the detent pawl and rotary latch is also designed to avoid false closing. With the corresponding size of the undercut the catch surface and opposing catch surface act in the manner of a key mechanism. The reset force of a reset buffer which is often assigned to the rotary latch and which accommodates the over-stroke of the rotary latch is designed to lead to the opposing catch surface on the detent pawl being exposed to force from the catch surface on the rotary latch, such that the detent pawl is drawn into the full engagement depth in the main catch of the rotary latch.
It is obvious that the aforementioned measure for preventing false closing adversely affects the ease of opening of the motor vehicle door lock in the same way. Otherwise it is generally such that the ease of opening also suffers from the fact that the path which the detent pawl must traverse for complete lifting from the main catch of the rotary latch (or its forward catch) is rather large due to the large engagement depth between the catch surface and the opposing catch surface.